200 Electrochemical Researches on 



third of red oxide of mercury, the mixture was placed oh a 

 plate of platina, a cavity was made in the upper part of it to 

 receive a globule of mercurv, of from fifty to sixty grains in 

 weight, the whole was covered by a film of naphtha, and the 

 plate was made positive, and the mercurv negative* by a 

 proper communication with the battery of five hundred. 



The amalgams obtained in this wav were distilled in 

 tubes of plate glass, or in some cases in tubes of common 

 glass. These tubes were bent in the middle, and the ex- 

 tremities were enlarged, and rendered globular bv blowing, 

 so as to serve the purposes of a retort and receiver. 



The tube after the amalgam had been introduced, was 

 filled with naphtha, which was afterwards expelled by boil- 

 ing, through a small orifice in the end coi -responding to the 

 receiver, which was hermetically sealed w hen the tube con- 

 tained nothing but the vapour of naphtha, and the amalgam. 



I found immediately that the mercury rose pure by distil- 

 lation from the amalgam, and it was very easy to separate a 

 part of it 3 but to obtain a complete decomposition was very 

 difficult. 



For this nearly a red heat was required, and at a red heat 

 the bases of the earths instantly acted upon the glass, and 

 became oxygenated. When the tube was large in propor- 

 tion to the quantity of amalgam, the vapour of the naphtha 

 furnished oxygen sufficient to destroy part of the bases : and 

 when a small tube was employed, it was difficult to heat the 

 part used as a retort sufficient to drive off the whole of the 

 mercurv from the basi.-, without raising too highly the tem- 

 perature of the part serving for the receiver, so as to burst 

 the tube*. 



In consequence of these difficulties, in a multitude of 

 trials, I obtained only a very few successful results, and4n 

 no case could 1 be absolutely certain that there was not a 

 minute portion of mercury still iri combination with the 

 metals of the earths. 



In the best result that I obtained from the distillation of 



* When the quantity of the amalgam was about fifty or sixty grains, I 

 found that the tube could not be conveniently less than one-sixth of an inch 

 \u diameter, and of the capacity of about half a cubic inch. 



the 



